PRINCIPLES PAVEMENT DESIGN

By

Sri. A. Ramesh, (Ph.D)

Objectives To understand the need for rational design

of Pavement To understand how pavements fail

functionally or structurally. Key parameters to be consider for design It makes us understand the differences of

different Pavement design approaches

For What Purpose Are Pavements Being Built And Where

Pavements is a structure which are intended to carry vehicular traffic

These pavements are provided atAir Ports Terminals Highways Terminals

Types of Pavements Un Surfaced

Earthen roads Gravel roads

Surfaced Bituminous Road Cement Concrete Road

Un Conventional Block Pavement

Flexible Pavements Earthen Roads Gravel Roads Bituminous Roads

Rigid Pavements Reinforced Concrete Plane Concrete Roads

Further Classification of Pavements

GRAVEL ROADS

Bituminous Pavement with Shoulder

Components of Flexible pavement

Load Dispersion in Flexible Pavements

Base

Black Topping

450

Sub Grade300mm

Sub Base

450

LOAD DISPERSION IN FLEXIBLE PAVEMENTS

Base

Black Topping

450

Sub Grade300mm

Sub Base

450

Base

Black Topping

450

Sub Grade300mm Sub Grade300mm

Sub Base

450450

LOAD DISPERSION IN FLEXIBLE PAVEMENTS

Rigid Pavement

Reinforced Cement Concrete Pavement Details

It is very challenging task compared to any other structure Complex loading

Complex behavior for various climatic condition

It is difficult in colleting information on performance modeling for various materials.

PAVEMENT DESIGN

DESIGN PARAMETER

Pavement Type No. Layers Layer Materials Joint Spacing for RCC

External Parameters

Sub grade Strength. Soil type, Strength, drainage Characteristics.

Traffic loading. No. Vehicles, type of vehicle, Speed, Load

Climatic Condition. Total Rainfall in year, Seasonal Distribution. Temperature (Max, Min, Daily Seasonal)

What Does Design means? For any given facility design is a process

of selecting appropriate values of parameters in such away that facility performs satisfactory.

Key words Design parameters Performance

PAVEMENT PERFORMANCE

Functional Performance Surface Characteristics eg. Pot holes,

Cracks, Rutting, Variation in longitudinal profile

“It is desirable to ensure that the surface characteristics are with in acceptable limits”

FATIGUE

Fatigue cracking

STRUCTURAL PERFORMANCE Mostly of the distress/ defects, Rutting are

caused by traffic loads

Some are also caused by non load associated factors Temperature, moisture, poor quality of

materials, inadequate maintenance. “ if the pavement shows load associated

distress it is considered to have failed structurally.”

Eg. Cracking, Rutting, Bleeding in Flexible Mud pumping, Blow up in CC Pavement

RUTTING

Rutting in wheel paths

Reflection cracking at PCC Joints

For What Pavement is to Be Design?

Functional Performance For road user FP is matter

Structural Performance For designer SP is matter

PERFORMANCE CRITERIA

Empirical Criteria Correlated to simple parameters like CBR,

Soil Index, Sub-grade. They do explain Load Vs Stress for different

materails. As result Empirical Methods cope up with

new materials Mechanistic Empirical Criteria

MECHANISTIC EMPIRICAL CRITERIA

Explain different phenomena (Stress, Strain Deflection) occurring in the pavement & the physical causes is explained using mathematical modeling.

Advantageous. Can Handel varying load condition, new materials. Contribution of different materials components is

better understood and thus optimal utilization is possible

More reliable and is called as rational.

Cannot cope with novel materials or pavement structures.

It is “like driving a car by only looking in the rear vision mirror, you could only be sure where you had been, but not where you were going”

Empirical Approach – Drawbacks

PERFORMANCE CRITERION IS HEART OF

PAVEMENT DESIGN

2. INPUT MATERIAL PROPERTIES CLIMATE INFORMATION

1. ASSUME PAVEMENT CONFIGURATION

3. CLIMATE MODELS HEAT TRANSFER MOISTURE EQUILIBRIUM INFILTRATION AND DRAINAGE

5. STRUCTURAL MODELS

4. INPUT TRAFFIC 6. PAVEMENT

RESPONSE

, , W

8. DISTRESS MODELS FATIGUE CRACKING, RUTTING, LOW TEMPERATURE CRACKING

7. DESIGN RELIABILITY

9. FINAL DESIGN

Figure 3.1: Calibrated mechanistic procedure for flexible pavement design.

SATISFACTORY

UN

SA

TIS

FA

CT

OR

Y

Design of Flexible Pavements

BUILDING BETTER ROADS-

BUILDING THE NATION